Liquid solutions comprising amine compounds or aqueous ammonia solutions are commonly used as solvents in processes used for industrial separation of acidic components such as H2S, CO2, COS and/or mercaptans from gas streams such as flue gas, natural gas, synthetic gas or other gas streams mainly containing nitrogen, oxygen, hydrogen, carbon monoxide and/or methane. The acidic components are often absorbed in the solvent in an absorption process or scrubbing process. After “scrubbing” of said acidic components by said solutions, contaminants, such as traces of ammonia, have to be removed from the gas stream in a separate process step.
The most commonly used process for this purpose is a wash or scrubbing step of the contaminants. In such a wash water step, the gas stream is scrubbed with water in a suitable contacting device. Typically, the water used to scrub the gas stream is either fresh water or very low NH3 content water obtained from a stripping process related to the treatment of the gas stream. After the gas stream is scrubbed with water, the water is 1) sent back to the stripping unit from which it was obtained or 2) simply mixed with the solution used in the main scrubbing process.
There are methods known wherein the efficiency of the system and methods are improved. In WO 2009/138363 it is disclosed a method for removal of contaminants from a gas stream by contacting the gas stream with CO2 containing liquid. The methods are said to be applicable for contaminants like ammonia, where the emission of the contaminants is reduced. Also in U.S. Pat. No. 5,378,442 there is described a method to contact CO2 containing liquid for recovering of ammonia present in the combustion exhaust gas.
Regeneration of used wash liquids in the scrubbing process, for example in a stripping unit, is generally energy intensive and by that an expensive process. Therefore, there is a constant need for processes that improve wash efficiency and/or reduce wash liquid consumption. Regeneration of used wash liquids may be accomplished via stripping where a particular component is stripped from a wash liquid to regenerate the wash liquid.